A Template-Based Approach to Describing Metamorphic Relations

Metamorphic testing enables the generation of test cases in the absence of an oracle by exploiting relations among different executions of the program under test, called metamorphic relations. In a recent survey, we observed a great variability in the way metamorphic relations are described, typically in an informal manner using natural language. We noticed that the lack of a standard mechanism to describe metamorphic relations often makes them hard to read and understand, which hinders the widespread adoption of the technique. In this paper, we propose a template-based approach for the description of metamorphic relations. The proposed template aims to ease communication among practitioners as well as to contribute to research dissemination. Also, it provides a helpful guide for those approaching metamorphic testing for the first time. For the validation of the approach, we used the proposed template to describe 17 previously published metamorphic relations from different domains and groups of authors, without finding expressiveness problems. We hope that this work eases the diffusion and adoption of metamorphic testing, contributing to the progress of this thriving testing technique.